Social support is an important factor in recovery from alcohol use disorders (AUDs). In particular, involving a concerned significant other (CSO) in treatment, leads to more positive outcomes. A specific form of CSO-involved treatment, Alcohol Behavioral Couple Therapy (ABCT), has strong empirical support for its efficacy. Little is known, however, about how and why ABCT leads to better outcomes of treatment. The overall objective of the proposed study is to better understand the mechanisms by which CSO-involved treatment is effective. Study aims are: (1) To see if CSO and dyadic behaviors at the beginning of ABCT predict Identified Patient (IP) drinking during treatment;(2) To see if CSO and dyadic behaviors change during ABCT;(3) To see if changes in CSO and dyadic behavior are associated with changes in IP drinking behavior during treatment;(4) To see if changes in CSO and dyadic behavior during treatment predict post-treatment IP drinking;(5)To see whether therapist behaviors predict drinking outcomes;(6) To test the effects of pretreatment and within treatments variables, including IP sex, baseline relationship functioning, and treatment compliance (attendance and homework) on treatment outcome. To accomplish these aims, existing audiotapes of 186 first session and 136 mid- treatment sessions from four randomized clinical trials of ABCT will be coded. Additional data on IP, CSO, and couple baseline characteristics, and within treatment and one-year follow-up data are available for all studies. Tapes will be coded using the Motivational Interviewing with Significant Others coding system to rate CSO and couple-level behavior;and the Treatment Integrity Rating System for ABCT to code therapist behavior. Results should contribute to improved treatment for patients with AUDS by: (1) providing information to clinicians to identify particularly positive or toxic behaviors at the start of treatment that would guide decisions about CSO-involvement in later sessions;and (2) providing information to clinicians about behaviors to target in CSO-involved treatment to maximize positive outcomes. PUBLIC HEALTH RELEVANCE: Alcohol use disorders exact a toll on the individual, family, and society. Development of more effective treatments is an important research goal. One promising approach is to involving family members in treatment - research consistently shows that family involvement leads to better outcomes. The proposed research is designed to provide better knowledge about of why family involvement is helpful in treatment, knowledge that should help clinicians to be more effective when families are involved in alcoholism treatment.